1. Field of the Invention
This invention relates in general to a multimedia communications, and more particularly to a method and apparatus for improving call setup efficiency in multimedia communication systems.
2. Description of Related Art
Of the communication tools found in most offices today, such as E-mail, fax machines, pagers, and cellular phones, videoconferencing has yet to make the short list. However, this is changing, as companies move to take advantage of lower system costs and emerging new standards. For example, videoconferencing over an enterprise IP network is very appealing. It makes better use of an organization""s finds rather than sinking additional investments in ISDN lines. Up to now, ISDN has been the only reliable way to connect video-enabled workstations and conference-room-based systems. However, the technology isn""t readily available, and it""s still expensive. Nevertheless, H.323-standard LAN-operable DVC (desktop videoconferencing) solutions are available.
The H.323 standards architecture specifies gateways and gatekeepers that enable connections among LAN-based DVC units, ISDN-connected H.320 units, analog telephone-connected H.324 devices, and ISDN and POTS telephones. One rapidly emerging branch of this market includes gateway and billing server systems devoted to Internet telephony.
The H.323 standard provides a foundation for audio, video, and data communications across IP-based networks, including the Internet. By complying to H.323, multimedia products and applications from multiple vendors can interoperate, thereby allowing users to communicate without concern for compatibility. H.323 will be the keystone for LAN-based products for consumer, business, entertainment, and professional applications.
More specifically, H.323 is an umbrella recommendation from the International Telecommunications Union (ITU) that sets standards for multimedia communications over Local Area Networks (LANs) that do not provide a guaranteed Quality of Service (QoS). These networks dominate today""s corporate desktops and include packet-switched TCP/IP and IPX over Ethernet, Fast Ethernet and Token Ring network technologies. Therefore, the H.323 standards are important building blocks for a broad new range of collaborative, LAN-based applications for multimedia communications.
The H.323 specification was approved in 1996 by the ITU""s Study Group 16. Version 2 was approved in January 1998. The standard is broad in scope and includes both stand-alone devices and embedded personal computer technology as well as point-to-point and multipoint conferences. H.323 also addresses call control, multimedia management, and bandwidth management as well as interfaces between LANs and other networks.
H.323 is the latest of the recommendations on the H.32X series which specifies standards for videoconferencing over a variety of networks. H.323 includes much of the work done since the approval of the H.320 recommendation in 1990, which is an specification for multimedia over circuit switched digital telephone networks. The H.32X is composed of the following recommendations:
H.320 allows videoconferencing over narrowband switched ISDN.
H.321 is for videoconferencing over broadband ISDN ATM LAN.
H.322 allows videoconferencing over Guaranteed bandwidth packet switched networks.
H.323 allows videoconferencing over non-guaranteed bandwidth packet switched networks.
H.324 is for videoconferencing over PSTN or POTS (the analog phone system).
The H.323 Protocol Stack supports many real time applications that the industry is eager to use through the Internet such as: Desktop Videoconferencing, Internet Telephony and Videotelephony, Collaborative Computing, Business Conference Calling, Distance Learning, Support and Help Desk Applications, etc. These applications already exist in the market, but most of them do not address the problem of how to run these applications over a packet switch network like the Internet and most corporate LANs which are based in the TCP/IP suite of protocols. With the pressure of the market to use this kind of applications over the Internet, H.323 emerges as a possible solution to the business needs.
H.323 defines four major components for a network-based communications system. FIG. 1 illustrates a H.323 system 100. In FIG. 1, the four major components of a H.323 system 100 are shown including their interaction with existing networks. These components interact with LANs that don""t provide QoS. The four components include Terminals 110, Gateways 120, Gatekeepers 130 and Multipoint Control Units (MCUs) 140.
These four elements 110-140 are specified only for the Application Layer of the Internet Layer Model. There is no specification about the lower layers (Transport, Network, Data link and physical layers). These characteristic makes H.323 flexible and allows H.323 devices to communicate with device of other networks.
H.323 Terminals 110 are the client software that runs in the end user computers that allow users to communicate in real time using all the power of multimedia. These terminals are also called Endpoints.
A Gateway 120 is a component of the H.323 specification that provides world wide connectivity and interoperability from LAN. That is, a Gateway 120 will allow computers connected to a LAN to communicate to regular phones 150 connected to the PSTN 152, to digital phones 154 (H.320 terminals) connected to an ISDN network 156. A gateway 120 also translates between different types of codecs used by different kinds of terminals, maps call signaling between Q.931 to H.225 and maps control signaling between H.242/H.243 to H.245.
In general, a Gateway 120 is a component that makes possible to interconnect a packet switched network with no QoS to other types of networks. If connections to different types of networks are not required, then a Gateway 120 is not required since terminals can communicate between them if they are on the same LAN. Terminals communicate with gateways using Q.931 and H.245 protocols.
A Gatekeeper 130 is an H.323 component that performs four basic functions:
Address Translation: It is the mechanism that allows to have different kinds addressing systems. For example, regular phone numbers (E.164 addresses) can be used in conjunction with e-mail addresses. The Gatekeeper 130 allows to communicate with terminals addressed in different ways.
Admission Control: The Gatekeeper 130 could reject calls from users. An user must be registered with the Gatekeeper 130 in order to complete a call.
Bandwidth Control: Networks managers can restrict the amount of bandwidth used for videoconference, which provide a way to control LAN traffic. The remaining of the bandwidth can be used then for web requests, e-mail, file transfers, etc.
Zone Management: The Gatekeepers 130 provide the functions of Address Translation, Admission Control and Bandwidth control for Terminals 110, MCUs 140 and Gateways 120 registered with the Gatekeeper 130 in its zone of control. This zone is called H.323 zone.
The functions of the Gatekeeper 130 are included in the Gateway 120 by most vendors, although they are logically separated and they perform different kind of functions.
The Multipoint Control Unit (MCU) 140 is a logical device that supports conferences between three or more endpoints. The MCU 140 typically is integrated with the implementation of the gateway, so in most implementations the MCU 140 won""t be a separate computer performing conferencing functions. Also, with a combined implementation of the functions of the MCU 140 with the functions of the gateway 120, conferences among participants of different networks (LAN and PSTN) will have better performance than divided implementations.
Call setup in H.323 systems requires the exchange of several messages between several entity pairs. The sequence of message exchanges is specified by H.323 and depends upon the presence or absence of gatekeepers for the calling and/or called endpoint and on the choice of direct/gatekeeper routed models. Nevertheless, the call setup time could be reduced and efficiency improved if the number of message exchanges could be reduced without sacrificing any of the call setup functionality.
If can also be seen that there is a need for a method and apparatus for improving call setup efficiency in H.323 systems.
To overcome the limitations in the prior art described above, and to overcome other limitations that will become apparent upon reading and understanding the present specification, the present invention discloses a method and apparatus for improving call setup efficiency in multimedia communication systems.
The present invention solves the above-described problems by performing call setup in H.323 systems using fewer message exchanges, thereby resulting in a more efficient call setup mechanism. Moreover, no call setup functionality is sacrificed by resorting to fewer message exchanges.
A method in accordance with the principles of the present invention includes placing a call at a first endpoint to a remote endpoint, requesting admission from a gatekeeper for the call, returning an accept message to the first endpoint, the accept message including a token for providing information to the remote endpoint alleviating the need of the remote endpoint to request admission from a gatekeeper, routing a setup message to the remote endpoint, the setup message including the token and completing a call setup based upon information in the token.
Other embodiments of a system in accordance with the principles of the invention may include alternative or optional additional aspects. One such aspect of the present invention is that the first endpoint and the remote endpoint are registered with a common gatekeeper.
Another aspect of the present invention is that direct call signaling is implemented by the first endpoint and the remote endpoint, the routing of the setup message being performed by transmitting directly to the remote endpoint the setup message including the token.
Another aspect of the present invention is that gatekeeper routed call signaling is implemented, the routing of the setup message is performed by routing the setup message including the token from the first endpoint to the common gatekeeper and routing the setup message including the token from the common gatekeeper to the remote endpoint.
Another aspect of the present invention is that the first endpoint is registered with a first gatekeeper and the remote endpoint is registered with a second gatekeeper.
Another aspect of the present invention is that the requesting admission from a gatekeeper for the call further includes requesting admission by the first endpoint from the first gatekeeper, analyzing by the first gatekeeper the admission request to determine if a criterion for the call is acceptable according to requirements local to the first gatekeeper, routing the admission request to the second gatekeeper when the first gatekeeper determines the criterion for the call is acceptable, analyzing by the second gatekeeper the admission request to determine if a criterion for the call is acceptable according to requirements local to the second gatekeeper and sending an admission confirmation including the token to the first gatekeeper when a required criterion for the call is determined to be acceptable according to the requirements local to the second gatekeeper.
Another aspect of the present invention is that the first and second gatekeepers implement direct call signaling, the routing of the setup message being performed by transmitting directly to the remote endpoint the setup message including the token.
Another aspect of the present invention is that the first gatekeeper implements direct call signaling and the second gatekeeper implements routed call signaling, the routing of the setup message is performed by transmitting the setup message including the token to the second gatekeeper and the second gatekeeper transmitting the setup message including the token to the remote endpoint.
Another aspect of the present invention is that the completing the call setup further comprises routing of the setup message by transmitting connect/facility messages from the remote endpoint to the second gatekeeper and transmitting the connect/facility messages to the first endpoint setup message from the second gatekeeper.
Another aspect of the present invention is that the first gatekeeper implements routed call signaling and the second gatekeeper implements direct call signaling, the routing of the setup message is performed by transmitting the setup message including the token to the first gatekeeper and the first gatekeeper transmitting the setup message including the token to the remote endpoint.
Another aspect of the present invention is that the completing the call setup further comprises routing of the setup message by transmitting connect/facility messages from the remote endpoint to the first gatekeeper and transmitting the connect/facility messages to the first endpoint setup message from the first gatekeeper.
Another aspect of the present invention is that the first gatekeeper and the second gatekeeper implement routed call signaling, the routing of the setup message is performed by transmitting the setup message including the token to the first gatekeeper, the first gatekeeper transmitting the setup message including the token to the second gatekeeper and the second gatekeeper transmitting the setup message including the token to the remote endpoint.
Another aspect of the present invention is that the completing the call setup further comprises routing of the setup message by transmitting connect/facility messages from the remote endpoint to the second gatekeeper, transmitting the connect/facility messages to the first gatekeeper from the second gatekeeper, and transmitting the connect/facility messages to the first endpoint setup message from the first gatekeeper.
Another aspect of the present invention is that the routing the admission request to the second gatekeeper further comprises routing the admission request through a cloud of gatekeepers.
Another aspect of the present invention is that the token comprises a transport address of the second gatekeeper.
Another aspect of the present invention is that the token comprises resource allocations for the call.
An alternative embodiment of the present invention includes sending a setup message from a first endpoint to a remote endpoint, requesting admission from a gatekeeper for the call, the request for admission including all information required for performing call setup, returning an accept message to the remote endpoint, the accept message indicating to the remote endpoint that the gatekeeper is implementing routed call signaling and including a transport address for the gatekeeper, and routing a facility message to the first endpoint informing the first endpoint of the transport address for the gatekeeper and that the call signaling channel is through the gatekeeper.
Another aspect of the present invention is that the first endpoint is not registered and the remote endpoint is registered with the gatekeeper.
Another embodiment of the present invention is a multimedia communications system, the multimedia communications system including a first endpoint for placing a call to a remote endpoint, and a gatekeeper, operatively coupled to the first endpoint, the gatekeeper performing address translation, admission control and bandwidth control, wherein the first endpoint requests admission from the gatekeeper for the call, the gatekeeper returns an accept message to the first endpoint, the accept message including a token for providing information to the remote endpoint alleviating the need of the remote endpoint to request admission from a gatekeeper, the first endpoint routes a setup message to the remote endpoint, the setup message including the token and the remote endpoint completes the call setup based upon information in the token.
These and various other advantages and features of novelty which characterize the invention are pointed out with particularity in the claims annexed hereto and form a part hereof. However, for a better understanding of the invention, its advantages, and the objects obtained by its use, reference should be made to the drawings which form a further part hereof, and to accompanying descriptive matter, in which there are illustrated and described specific examples of an apparatus in accordance with the invention.